Circuits for controlling electric locks on railway track switches



July24, 1951 c. w. FAILOR CIRCUITS FOR CONTROLLING ELECTRI LOCKS ON RAILWAY TRACK SWITCHES Filed Feb. 14, 1948 IN V EN TOR.

ATTOHIVE'Y @w v an Em R M &w I. 5 K A Q n gm N 551w E fi mm w Patented July 24, 1951 NI TED "STAIES CIRCUITS "FGR GONTRDLLING ELECTRIC LGCKS N? RAILWAY TRACK SWITCHES Charles W. Failor, Forest 'liillspl 'au assignor to The Union Switch '& Signal Company, Swissvale, Pa, a corporation of Pennsylvania Appl-icationFebruary 14, 1948. Serial in. arts My invention relates to railway .traflic control- 5 Claims. (01. 2465-460) ling. apparatus, and more particularly to improved apparatus for controlling electric switch locks for safeguarding the operation of outlying hand thro-W track switches.

v An outlying. track switch of the type contemplated is to be understood to be one leading to an industrial siding or the like and intended. primarily .for operation by the crew of a train-doing local. switching, after obtaining permission by telephone or otherwise, from the dispatcher or central o'fiice operator. Such switches are 1usu-. allylat a distance from any existing interlocking plant and are at locations having no relation to the proper location. of the blocksign'als for protecting main line train movements. ,These switches must be free to be operated at times when there is train at the switch so the usual methods of safeguardingtrain movements over track switches-located within interlocking limits are not applicable.

One-object of my invention .is to provide improved switch lock control means incorporating means for insuring that the signal. at the entrance tothe bloclz sectionincluding the switch will be cleared'only when theswitcn is locked in its normalposition, and for controlling the signal to stop in. order. to allow the switch to be unlocked in responseto operation of the associated time element device.

Another object of my invention is .to provide an improved system of 'thetype described which is arranged sov that a switch maybe unlocked without delay to permit a train on a, siding to enter the main tra'clr if the main trackwithin apredetermined distance of the switch is not occupied.

A further object of my invention is .toprovide an 'irriproved system of the type described which arranged so that when the maintrack within a predeterminedIdistance'of a switch is occupied, the switchcan be unlocked to permit a, train on a siding to enter the main track only after the expiration of a time interval long enough to'allow'the train on 'the'main track to stop before reaching the switch, or if unable to stop, to overrun the switch and thus prevent movement of the switch in front of the train.

Another object of the invention is to-provide an improved switch lock control system which is arranged so that the lock is controlled entirely.

by one of the train crew at the switch.

A further objectof the invention is to provide improved means of the type described which is adapted 'for use where there are 'a'plurality o switches within single track section.

"Another object of the invention-is to provide improved means of the type described which is arranged so that after a switch has been unlocked it will" remain unlocked until it is certain that itis intended that the switch is tobe'l'ocked.

Kiur'ther object of the invention is to provide improved means of the type described which is arranged, so that after a switch has been unlocked it will not be inadvertently locked before a train has completed its movements overthe switch.

Another. object .of the invention is to provide improvedswitch lock control means which reduces to a minimum .the number of line wires which. mustbe provided between the switch and thel'first signal in the rear of the switch.

"Other objects of the invention and features of novelty will be apparent from the following description taken in connectionwith the accompanying drawing.

In the drawing the single figureis a diagram showing a stretch of railway track including'a track section in which there are two track switches equipped with locks governed by means provided by thisinvention. I In practicing my invention, I provide a line circuit which extends from the entrance end of a track section to the switch farthest from the is made to unlock the switch;

entrance end of the section, and I provide means atth-e entrance end of the section 'for at times supplyingenergy to this line circuit. In addition, I provide means at each switch for releasing the lock for the switch when energy is received over this line circuit; When a signal control relay governed 'bytraffic conditions in the stretch is picked up energy is supplied to this line circuit only when an'appro'ach relay is picked up to show that'the'track stretch leading to the section is uno ccupiedior a predetermineddistance. Under these conditions, therefore, the switch maybe unlocked without delay to. permit a train on the siding to enter'the track. When the. signal control relay is released energy is supplied to a time elementrelay andwhen it-picks up energy issuppliedto'theline circuit; I f :Each switch lock includes means rendered'effective during a preliminary part of the operationof unlocking of the switch for shuntingthe track'circuit-of the track section including the switch to thereby release the signal control relay and cause ehergytobe supplied to the time elementrelay'; Accordingly, when the approach relayis released, and it isdesired to reverse the vs'witch'to permit atrain on the siding'to enter switch is to' 'be lockedeven though the "supply traflic normally moves in the direction indicated by the arrow, that is, from left to right. The track rails I and 2 are divided by insulated joints 3 into the customary track sections for signaling purposes. One complete track section together with portions of the adjoining track sections is shown. The track section which is shown in the drawing is divided by insulated joints 3 into three subsections which are designated 5CT, 5BT and EAT. These subsections are separated by short releasing track sections AWT and BWT each of which is provided with a track circuit including a track relay. The releasing sections AWT and BWT are located immediately in advance of the track switches AW and BW which lead to side tracks.

The track rails of the subsections on opposite sides of each short releasing track section are connected together by wires governed by contacts of the track relay of the releasing section so that the three subsections 5CT, 531 and SAT together form one track circuit. This track circuit includes a code following track relay 5TB which is connected across the section rails at the entrance end of the section and is operated by energy supplied over the section rails from the track battery 5TB at the exit end of the section. The supply of energy from the battery 5TB to the section rails is governed by a contact of the transmitter relay 5GP, and this relay may be operated by means well known in the signaling field so as to at times cause energy of '75 code frequency and to at other times cause energy of 180 code frequency to be supplied to the track rails depending on trafiic conditions in advance.

The track relay 5TB, governs the supply of energy to the slow release relays 5F? and 5H, and also governs the supply of energy to the primary winding of the decodin transformer 5DT from which energy is at times supplied through a resonant rectifier unit ISODU to the relay 5D. The relays 5H and 5D cooperate to control the supply of energy to the lamps of the signal 5S which governs entrance of traffic into the section.

An approach relay SAP is associated with relay 5H and is governed by traffic conditions in section 6T so as to be picked up only when section GT is unoccupied. The relay BAP may also be controlled by traffic conditions in the rear of section ST. The means for controlling relay GAP is not a part of this invention and this relay may be governed in any suitable manner.

A time element relay 5TB is located at the entrance end of the section and has a winding to which energy is supplied when the relays 5F]? and 5H are released. The relay STE has normally closed checking contacts I0 and II which are opened as soon as energy is supplied to the relay winding, and has normally open contacts l2 and [4 which become closed only after energy has been supplied to the relay winding for a substantial time interval, such as six minutes.

A line circuit consisting of line Wires l6 and 11 extends from the entrance end of the section to the switch BW, and, as hereinafter explained, energy is at times supplied to this line circuit over contacts of the relays at the entrance end of the section.

Each of the track switches AW and BW is provided with an operating mechanism comprising a hand throw switch stand, which may, for example, be of the type shown in Letters Patent of the United States No. 2,184,870, issued to Herbert L. Bone and Kenneth J. J. McGowan, on December 26, 1939, for Railway Switch Operating Mechanisms. The operation of each switch is governed electrically by an electric switch lock controlled by a lock magnet AWL or BWL. The electric lock may be applied directly to the lock rod of' the switch in a wellknown manner, but preferably it is applied to the operating lever of the switch stand.

The electric switch locks may be of the type disclosed in Letters Patent of the United States No. 1,126,834, issued to Walter P. Neubert and William E. Smith, on February 2, 1915 for Electrio Switch Locks. For an understanding of the details of operation of the locking mechanism reference may be made to this patent, but for an understanding of this invention it is believed that it will suffice to point out that the operating lever of each switch stand is normally locked mechanically in a position to maintain the associated track switch locked normal, by means of a padlock. More particularly, a lever latch attached to a segment 25 is held in its locking position by the bail of a padlock 50, as indicated diagrammatically in the accompanyin drawing, and as shown in detail in Fig. 1 of the Neubert et al. patent. To unlock the switch, the padlock must first be removed by one of the train crew to permit the segment 25 to be moved a short distance to a position to engage the locking dog 21 and close the contacts 46a4'l.a, 46b-41b, and 460-410. Then if trafiic conditions are such that it is proper to unlock a switch, the winding of the associated lock magnet will become energized to lift the locking dog 21, permitting the segment 25 to be moved to its full reverse position in which the associated switch operating lever is free to be operated. The movement of a switch lever toward its reverse position projects one end of a rod 39, arranged as shown in Figs. 1, 5, and 6 of the Neubert and Smith patent, into the path of the lever latch with the result that the segment 25 is held reversed and cannot be restored to its normal position as long as the switch operating lever is out of its normal position.

It is also to be understood that each switch stand is equipped with the usual switch circuit controller and point detector having a movable contact 82 which is open only when the switch points and the operating lever for the switch are both in their normal positions.

Each switch has associated therewith a control relay WAR which governs the supply of energy to the winding of the associated lock magnet. Each switch control relay is provided with a pickup winding to which energy is supplied from the line wires l6 and 11. Each switch control relay is also provided with a second or holding winding to which energy is supplied from a suitable local source of direct current, such as a storage battery, 1 not shown, the terminals. aorzwhich are designated B andC in the drawing; 1

The equipment is shown in the condition which itjassumes when the track stretchi'svacant and the switches AW and BWare locked normal. As the switches are normal the contacts 32ers open and. do not shunt .the vtrack rails, andcas the switches are locked the contacts dta4la ofithe switch locks are open and'do not'shunt thetrack rails 'while the other contacts of the switch locks are open andinterrupt the circuits for supplying energy to the-switch lock windings. Accordingly, the locking dogs 'Zl are released and prevent movement of the segments -:25 tounlock the switch operating levers.

, As the contacts of the switch circuit controllers and of the switch locks are open, coded energy supplied from battery 5TB as a result ofoperation :of the relay 5GP feeds over the section rails and over the wires Icy-passing the short releasing track sections AWT and BWT to the winding of the track relay 5TH. As a result of the supply of coded energy to the winding of relay 5TB the relay contact picks up and releases. During the picked-up periods of contact 28 of relay 5TB energy. is supplied to relay EFP and its contacts are picked up with the result that during the re-' leased periods of the relay 5TB energy is supplied to relay-5H over the circuit which includes back contact 23 of relay 5TH, back contacts Ill and II of relay STE in series, and front contact 2! of relay EFF. The relays 5F? and 5H are snubbed by rectifiers so that they are slow enough in releasing to remain picked up as long as the relay 5TH is responding to coded energy.

In addition, as a result of code following operation of the track relay ET? the two portions of the primary winding of the decoding transformer EDT are alternately energized and energy is induced in the transformer secondary winding. When the relay 5TB is operated by coded energy of 180 code frequency, as is the case when the track stretch is vacant, the energy induced in the secondary winding of the transformer EDT is of such frequency that suf icient energy is supplied through the resonant rectifier unit IBtDU to pick up the contacts of relay 5D. As the relays 5H and 5D are picked up an obvious circuit is established for supplying energy to the green or clear lamp of the signal ES. 7

g The relay 51-1 may be employed in th manner well known in the art to govern the supply of coded energy to the rails of section 61, and thus controlapproaching trafiic in accordance with r tranic conditions in the section which includes the track. switches.

.As the relays 5F? and circuitof .thetime element relay :5TE is open at back contact 22 ,of relay 5H and at back contact 23 of relay EFF. Accordingly, the contacts of relay ETE are released at this time. I As the track stretch is assumed to be vacant the approach relay 5A? is pickedup with the result that terminal B of the local source is connected over front contact 22 of relay 5H and front contact 353 of relay GAP to'line wire I ii, and terminal C of the local source is connected over front contact 3! of relay EFF and front contact 32 .of relay BAP to line wire l1. Accordingly, energy is supplied to the line wires l6 and I! so that energy is supplied from these line wires to the pick-up windings of the relays AWAR and BWAR and their contacts are picked up, but their contacts do not establish the circuits for supply- EH are poked up the ing energy-to the win .lngs of thejswitch.locks and theyremain'deenergized. 1

With the equipment :in the condition illustrated. in the drawing, a: switchuilock: maybereleased without delay to permit a switch to be reversed to enablea train'ong'a side track to enter theamain track. If, vfor example, atrain-rnan wishes to reverse switch AW to permit 'a train on the sidingtoenter the main .track,.he will remov the pad-.-

lock from the .lockAWL. Vi hen therbail ofithe:

cuit to the upper or pick-up winding of the relay Accordingly, the relay: contacts are maintained picked up by energy supplied to the relay holding winding after the supply 501? energy to. the relay pick-up winding is outed. -As long as the contacts of relay AWAR remain picked up energ issupplied to the relay holdingwindingandalso tothe .w-inding of the lock AWL. The energysupplied to the windingiof the lock AWL causes-the locking -dog :27 to be lifted out of the path of the segment 25 and permits the segment to moi/etc its iullreverse position in which the" associated switch lever is free to be operated.

In addition, when the contacts 46 and "41 0f the switch lock-AVJL close, contacts-46a-47a establish a connection between'the'track rails which shunts the track relay ETR. Accordingly;

the track relay 5TB, remains released and relays 5FP, 5H, and 5D become released. Asa result of release of relays 5FP and 5H the supply of energy to the line wires 16 and i1 is interrupted, but'as explained above, energy is supplied to the holding winding of the relay AWAR before the supply of energy over the line wires l6 and I! to the relay pick-up winding is cut off so-the relay AWAR remains picked up and maintains the supply of energy to the winding of the lock AWL. On interruption of the supply of'energ'y to the line wires [6 and I! the Supply of energy to the pick-up winding of relay BWAR iscut off and the contacts of thisrelay release and prevent energization of the associated lock BWL.

On release of relay 51-1 the circuit'of the red or stop lamp R'of the signal 58 is established, and on release of relays 5F? and 5H the circuit for supplying energy to the winding of the time element relay STE is established and its contacts become picked up. The back contacts 10 and ll open promptly-on the supply of energy to'the relay winding, and when open interrupt the circuit of relay 5H to hold the signal 58 at fstop.

The contacts I2 and. M of relay STE "become closed only after energy has been "supplied to the relay winding for a substantial time'interval, such as sixminutes. When contacts 12 "and l4 of relay 5TET become closed connections are established for supplying energy to the line wires l6 and I! as long as relays 5F? and Eli are released. When'energy is supplied to wires t6 and I1 energy is supplied therefrom to the pick-up windings of the relays AWAR. andBWAR. 'As the contacts'of relay AWAR are picked up the supply of energy to the relay pick-up Winding has no effect, but the energy supplied to the pick-up winding of relay BWAR picks up the relay contacts to permit energy to be supplied to the associated look if it is desired to move the switch BW.

As soon as the operating lever of the switch AW is moved away from its normal position, the rod 39 moves into the path of the segment 25 and holds it reversed to thereby hold the contacts 46 and 41 closed. In addition, when the operating lever for the switch AW is moved the contact 82 governed thereby establishes a connection between the track rails I and '2 to thereby shunt the track relay STR and prevent its operation. This insures that the signal SS is held at stop as long as the switch AW is not in its normal position.

After the switch AW is reversed the train on the siding may enter the main track. As soon as the train enters section AWT the relay ATR releases and its contacts interrupt connection between the portions of the track rails on opposite sides of the section AWT and shunt the portion of the rails at the left of this section. This insures that relay STR will remain released and that signal SS is held at stop.

When the operating lever for the switch AW is restored to its normal position, the contact 82 associated with this switch is opened.

When the operating lever of the switch AW is restored to its normal position, the contacts 46-41 of the associated switch lock are unaffected and remain closed. Hence the supply of energy to the holding winding of relay AWAR, and to the winding of the lock AWL, is maintained and the lock AWL remains released to permit operation of the switch if this is desired. The arrangement of the apparatus is such, therefore, that once an unlock of aswitch is secured, the switch will not be inadvertently locked when the operating lever for the switch is restored to normal.

When the train completes its movementsv over the switch AW, one of the crew replaces the padlock Si! on the lock AWL. When the padlock is replaced on the lock AWL the seg ment 25 of the lock is restored to its normal position and the contacts 46-41 of the lock are opened. When contacts Mia-41a are opened the connection between the track rails is interrupted, but at this time the presence of the train in the track stretch prevents the track relay STR from operating and thus holds signal SS at stop.

In addition, when contacts 4617-411) and 460-- 410 are opened the circuit for supplying energy to the holding winding of relay AWAR, and to the winding of the lock AWL, is'interrupted. Accordingly, the contacts of relay AWAR release and the locking dog 21 of the lock AWL released.

When the train under consideration vacates the track section coded energy supplied from battery STB feeds over the section rails and operates the track relay STR to pick up relay SFP' so that its contact 23 interrupts the circuit of the Winding of relay STE with theresult that its contacts release. When the contacts of relay STE release, contacts l0 and II in the circuit of relay SH are closed and on continued code.

folowing operation of relay STR energy is supplied to relay SH and its contacts pick up to additionally interrupt the circuit of relay STE. In addition, when the relay SI-I picks up one of its contacts interrupts the circuit of the red lamp R of signal SS and establishes the circuit gov- 8 erned by a contact of relay SD for supplying energy to the yellow or the green lamp of signal SS.

As soon as relay SFP picks up its contact 3| interrupts the circuit governed by front contacts of relay STE. for supplying energy to the line Wires [6 and 11. This circuit is additionally interrupted on release of contacts 12 and I4 of relay STE, and on picking up of contact 22 of relay SH. When relays SFP and SH are picked up energy may be supplied over their front contacts and over front contacts of relay SAP to the line wires 16 and I1, and thus to the pick-up windings of the relays AWAR and BWAR so the contacts of these relays pick up. When this occurs, the equipment is again in substantially the condition in which it is illustrated in the drawing.

The equipment operates so that if, at the time an attempt is made to unlock a switch to permit a train on a siding to enter the main track, the portion of the track stretch within a predetermined distance in the rear of the switch is occupied so that relay GAP or relay SH is released. the lock may be released only after the expiration of the time interval determined by relay STE. This time interval is long enough to enable an approaching train to stop before reaching the switch, or to overrun the switch and thus prevent opening of the switch in front of the train.

When relay SAP is released its contacts 30 and 32 interrupt the connections including front contacts of relays SF]? and SH and over which energy is supplied to line wires l6 and 11. Similarly, when relay SH is released the connections for supplying energy to the line wires 18 and 11 are interrupted. Accordingly, the relays AWAR and BWAR are released and their contacts interrupt the circuits for supplying energy to the relay holding windings and to the windings of the switch locks.

If an attempt is now made to unlock the lock AWL, and the padlock is removed from this look, the segment 25 will move to a position to cause the associated contacts 46 and 41 to close. When contacts 4619-411) and 460-410 close, energy is not supplied to the holding winding of relat AWAR and to the winding of the lock AWL since the circuit of these windings is open at the contacts of relay AWAR. When contacts 46a,41a close, a connection is etablished between the track rails so the track relay STR ceases to operate and relays SFP and SH release, if they are not already released, to establish the circuit of V the winding of relay STE and to also cause signal SS to display its stop indication. As soon as energy is supplied to relay STE its contacts In and H pick up to interrupt the circuit of relay 5H and hold the signal SS at stop. The contacts l2 and [4 of relay STE do not become closed until energy has been supplied to the winding of relay STE for a substantial time interval, and until the contacts 12 and i4 become closed, the supply of energy to the line wires 16 and I1 is interrupted. As long as the supply of energy to the line wires 16 and I1 is interrupted the relay AWAR is released and prevents the supply of energy to the winding of the lock AWL.

When the contacts l2 and 14 of relay STE become picked up energy is supplied to the line wires 18 and I1 and, therefore, is supplied from these wires to the pick-up winding of relay AWAR and its contacts pick up to establish the circuit for supplying energy to the relay holding winding and. to the winding of the lock AWL. The

a .9 I switch AW may now be moved, and the operation of the equipment at this time is the same as previously described in detail and need not be repeated.

This equipment is also arranged so that a switch may be unlocked without delay to permit a train on the main track to-enter a siding.

When a train on the main track advances into section ECT the track relay TR releases and remains released so that relays 5FP and 5H become released and cause signal ES to display its stop indication.

When the train advances into section AWTthe relay ATR releases and its back contacts 33 and 34 in the connections for supplying energy from the local source to the lower winding of relay AWAR,'and to the winding of the lock AWL, are closed. The circuits for supplying energy to the lower winding of relay AWAR and tothe winding of the lock AWL are complete as soon as the padlock is removed from the switch lock so that contacts 48b4lb and 460-410 become closed. Hence the lock is released promptly and the switch may be reversed without delay to permit .the'train to enter the siding.

When relay AWAR picks up its contacts establish connections to maintain the supply of energy to the relay holding winding, and to the winding of the lock AWL, in the event that section AWT is vacated and relay ATR picks up.

The operation of the equipment after movement of the switch, and after the train vacates the main track and the switch is restored to normal,is similar to that described in detail above and need not be repeated.

'As explained above, when a'train on the main track enters section 5CT, the relays 5FP and 5H release and establish the circuit for supplying energy to the winding of the relay 5TB If the train occupies the section long enough, the contacts l2 and Id of relay STE will become picked up and complete the connections for supplying energy to the line wires l6 and I! with the result that energy is supplied to the pick-up windings of relays AWAR and BWAR and their contacts are picked up to cause energy to be supplied to the winding of a look as soon as an attempt is made to unlock a switch. It is proper for a switch to bev unlocked under these conditions as the train in the section will have stopped or will be moving at such a low speed that the switch will not be a hazard. The arrangement just described enables a switch lock to be released in the event the equipment for a short releasing section is not functioning properly, or if these sections are not provided.

The equipment associated with switch BW opcrates in substantially the same manner as the equipment associatedwith switch AW and a detailed explanation of its operation is unnecessary.

Although I have herein shown and described only one form of switch lock control means embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

In combination with a section of railway track including a hand throw switch, means comprisinga mechanical lock and an electric lock for preventing the hand operation of said switch,

said section being provided with a track circuit including track relay means which is energized in response to energy supplied over the section rails, a signal governing entrance of traiiic into said section,.said signal being governed by said track relay means so as to display a permissive or a stop indicationaccording as said track relay means is energized or deenergized, an approach zone including at least one track section located in approach to said signal, an approach relay governed by trafiic conditions in said approach zone so as to be energized only when said approach zone is unoccupied, a time element device having normally open contacts which become closed only after energy has been supplied to the winding of said device for a substantial time interval, means effective when said'track relay means is deenergized for supplying energy to said time element device, a line relay associated with said switch, means for supplying energy to said line relay when said track relay means is energized provided said approach relay is energized, means for also supplying energy to said line relay when said track relay means is deenergized provided the contacts of said time element device are closed, means at said switch effective when said mechanical lock is released for preventing the supply-oi energy over the rails of said section to said track relay means, and means at said switch effective when said mechanical lock is released provided said line'relay is energized for supplyingenergy to said line relay and for also supplying energy to said electric lock to unlock said switch.

2. In combination with a block section of railway track including a hand throw switch, means comprising a mechanical lock and an electric lock for preventing the hand operation of said switch, said section being provided with a track circuit including track relay means at one end which is energized in response to energy supplied over the section rails, a signal at said one end governing entrance of trafiic into said section, said signal being governed by said track relay means so as to display a permissive or a stop indication according as said track relay means is energized or deenergized, an approach zone including at least one track section located in approach to said signal, an approach relay governed by trafdc conditions in said approach zone so as to be energized only when said approach zone is unoccupied, a time element device having normally open contacts which become closed only after energy has been supplied to the winding of said device for a substantial time interval, means effective when said track relay means is deenergized for supplying energy to said time element device, a line circuit extending from said signal to said switch, means for supplying energy to said line circuit when said track relay means is energizedprovided said approach relayis energized, means for also supplying energy to said line circuit when the normally open contacts of said time element device are closed, means at said switch effective when said mechanical lock is released for cutting off the supply of energy over the rails of said section to said track relay means, and means at said switch effective when said mechanical lock is released for supplying energy to said electric lock to unlock said switch provided energy is received at said switch over said line circuit.

3. In combination, a section of railway track through which traiiic normally moves in a selected direction, said track section including a hand throw switch at an intermediate point in said section, said track section being divided into aplurality of portions including a detector portion adjacent saidswitch, said detector portion being provided with a track circuit including a track relay, said track section being provided with a track circuit including track relay means at the entrance end of said section energized in response to energy which is supplied over the section rails only when the entire section is unoccupied, a signal governing entrance of traffic into said section, said signal being governed by said track relay means so as to display a permissive or a stop indication according as said track relay means is energized or is deenergized, an approach zone including at least one track section in approach to said signal, an approach relay governed by'traffic conditions in said approach zone so as to be energized only when said approach zone is unoccupied, a time element device having normally open contacts which become closed only after energy has been supplied to the winding of said device for a substantial time interval, means effective when said track relay means is deenergized for supplying energy to said time element device, a line relay assoriated with said switch, means for supplying energy to said line relay when said track relay means is energized provided said approach relay is energized, means for also supplying energy to said line relay when the contacts of said time element device are closed, an electric lock normally effective to lock said switch inits normal position as required for traffic movements through said section, a manually operable mechanical lock for preventing the operation or" said electric lock, means at said switch effective when said mechanical lock is released for cutting 01f the supply of energy over the rails of said section to said track relay means, and means at said switch efiective when said mechanical lock is released for supplying energy to said electric lock to unlock said switch provided said line relay is energized or the track relay for said detector portion is released.

4. In combination, a section of railway track through which trainc normally moves in a selected direction, said track section including a hand throw switch at an intermediate point in said section, said track section being divided into a plurality of portions including a detector portion adjacent said switch, said detector portion being provided with a track circuit including a track relay, said track section being provided with a track circuit including track relay means at the entrance end of said section energized in response to energy which is supplied over the section rails only when the entire section is unoccupied, a signal governing entrance of traffic into said section, said signal being governed by said track relay means so as to display a permissive or a stop indication according as said track relay means is energized or is deenergized, an approach zone including at least one track section in approach to said signal, an approach relay governed by trairic conditions in said approach zone so as to be energized only when said approach zone is unoccupied, a time element device having normally open contacts which become closed only after energy has been supplied to the winding of said device for a substantial time interval, means efifective when said track relay means is deenergized for supplying energy to said time element device, a line relay associated with said switch, means for supplying energy to said line relay when said track relay means is energized provided said approach relay is energized, means for also supplying energy to said line relay when the contacts of said time element device are closed, means at said switch effective when said mechanical lock is released for cutting off the supply of energy over the rails of said section to said track relay means, an electric lock normally effective to lock said switch in its normal position as required for traffic movements through said section, a manually operable mechanical lock for preventing the operationof said electric lock, means at said switch effective when said mechanical lock is released provided said line relay is energized for supplying energy to a winding of said line relay to maintain said line relay energized, and means at said switch efi'ective when said mechanical lock is released provided said line relay is energized or the track relay of said detector portion is released for supplying energy to said electric lock to unlock said switch.

5. In combination, a section of railway track through which traffic normally moves in a selected direction, said track section including a hand throw switch at an intermediate point in said section, said track section being divided into a plurality of portions including a detector portion adjacent said switch, said detector portion being provided with a'track circuit including a track relay, said track section being provided with a track circuit including a track relay means at the entrance end of said section energized in response to energy which is supplied over the section rails only when the entire section is unoccupied, a signal governing entrance of traffic into said section, said signal being governed by said track relay means so as to display a permissive or a stop indication according as said track relay means is energized or is deenergized, an approach zone including at least one track section in approach to said signal, an approach relay governed by trainc conditions in said approach zone so as to be energized only when said approach zone is unoccupied, a time element device having normally open contacts which become closed only after energy has been supplied to the winding of said device for a substantial time interval, means effective when said track relay means is deenergized for supplying energy to said time element device, a line circuit extending from said signal to said switch, means effective when said track relay means is energized provided said approach relay is energized for supplying energy to said line circuit, means effective when the contacts of said time element device are closed for also supplying energy to said line circuit, an electric lock normally effective to lock said switch in its normal position as required for trafiic movements through said section, a manually operable mechanical lock for preventing the operation of said electric lock, means at said switch effective when said mechanical lock is released for supplying energy to said electric lock to unlock said switch provided energy is received at said switch over said line circuit, and means at said switch effective when said mechanical lock is released for also supplying energy to said electric lock to unlock said switch provided the track relay of said detector portion is released.

CHARLES W. FAILOR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,241,614 Pelikan May 13, 1941 2,365,344 Judge Dec. 19, 1944 2,367,723 Haines Jan. 23, 1945 2,404,303 Law July 16, 1946 

